Integrated circuit package and method

ABSTRACT

In an embodiment, a device includes: an integrated circuit die; a redistribution structure over a front-side surface of the integrated circuit die; a socket over the redistribution structure; a mechanical brace over the socket, the mechanical brace having an opening exposing the socket, edge regions of the socket overlapping edge regions of the mechanical brace at the opening; a first standoff screw disposed in the edge regions of the mechanical brace, the first standoff screw physically contacting the socket, the first standoff screw extending a first distance between the socket and the mechanical brace; and a bolt extending through the mechanical brace and the redistribution structure.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application No. 62/775,506, filed on Dec. 5, 2018, which application is hereby incorporated herein by reference.

BACKGROUND

As semiconductor technologies continue to evolve, integrated circuit dies are becoming increasingly smaller. Further, more functions are being integrated into the dies. Accordingly, the numbers of input/output (I/O) pads needed by dies has increased while the area available for the I/O pads has decreased. The density of the I/O pads has risen quickly over time, increasing the difficulty of die packaging.

In some packaging technologies, integrated circuit dies are singulated from wafers before they are packaged. An advantageous feature of this packaging technology is the possibility of forming fan-out packages, which allow the I/O pads on a die to be redistributed to a greater area. The number of I/O pads on the surfaces of the dies may thus be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a cross-sectional view of an integrated circuit die, in accordance with some embodiments.

FIGS. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 illustrate various views of intermediate steps during a process for forming a package component, in accordance with some embodiments.

FIGS. 13 and 14 illustrate various view of a process for securing a package component between a thermal module and a mechanical brace, in accordance with some embodiments.

FIGS. 15, 16, 17A, 17B, 18A, 18B, 18C, and 19 illustrate various aspects of a mechanical brace, in accordance with some embodiments.

FIG. 20 illustrates a cross-sectional view of module installation in a system-on-wafer assembly, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

In accordance with some embodiments, a system-on-wafer assembly is formed by clamping a package structure between a thermal module and a mechanical brace. The mechanical brace includes standoff screws. The clamping is performed by initially fastening the thermal module and mechanical brace with a low torque. The standoff screws are then adjusted to fill gaps between the mechanical brace and package structure. By increasing the mechanical support, the mechanical brace may exert a more uniform pressure profile on the package structure and thermal module, thereby increasing the thermal dissipation for the package component.

FIG. 1 illustrates a cross-sectional view of an integrated circuit die 50, in accordance with some embodiments. The integrated circuit die 50 will be packaged in subsequent processing to form an integrated circuit package. The integrated circuit die 50 may be a logic die (e.g., central processing unit (CPU), graphics processing unit (GPU), system-on-a-chip (SoC), application processor (AP), microcontroller, etc.), a memory die (e.g., dynamic random access memory (DRAM) die, static random access memory (SRAM) die, etc.), a power management die (e.g., power management integrated circuit (PMIC) die), a radio frequency (RF) die, a sensor die, a micro-electro-mechanical-system (MEMS) die, a signal processing die (e.g., digital signal processing (DSP) die), a front-end die (e.g., analog front-end (AFE) dies), an application-specific die (e.g., an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc.), the like, or combinations thereof.

The integrated circuit die 50 may be formed in a wafer, which may include different device regions that are singulated in subsequent steps to form a plurality of integrated circuit dies. The integrated circuit die 50 may be processed according to applicable manufacturing processes to form integrated circuits. For example, the integrated circuit die 50 includes a semiconductor substrate 52, such as silicon, doped or undoped, or an active layer of a semiconductor-on-insulator (SOI) substrate. The semiconductor substrate 52 may include other semiconductor materials, such as germanium; a compound semiconductor including silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. Other substrates, such as multi-layered or gradient substrates, may also be used. The semiconductor substrate 52 has an active surface (e.g., the surface facing upwards in FIG. 1), sometimes called a front side, and an inactive surface (e.g., the surface facing downwards in FIG. 1), sometimes called a back side. Devices may be formed at the front surface of the semiconductor substrate 52. The devices may be active devices (e.g., transistors, diodes, etc.), capacitors, resistors, etc. An interconnect structure is over the semiconductor substrate 52, and interconnects the devices to form an integrated circuit. The interconnect structure may be formed by, for example, metallization patterns in dielectric layers on the semiconductor substrate 52. The metallization patterns include metal lines and vias formed in one or more low-k dielectric layers. The metallization patterns of the interconnect structure are electrically coupled to the devices of the semiconductor substrate 52.

The integrated circuit die 50 further includes pads 62, such as aluminum pads, to which external connections are made. The pads 62 are on the active side of the integrated circuit die 50, such as in and/or on the interconnect structure. One or more passivation films 64 are on the integrated circuit die 50, such as on portions of the interconnect structure and pads 62. Openings extend through the passivation films 64 to the pads 62. Die connectors 66, such as conductive pillars (for example, formed of a metal such as copper), extend through the openings in the passivation films 64 and are physically and electrically coupled to respective ones of the pads 62. The die connectors 66 may be formed by, for example, plating, or the like. The die connectors 66 electrically couple the respective integrated circuits of the integrated circuit die 50.

Optionally, solder regions (e.g., solder balls or solder bumps) may be disposed on the pads 62. The solder balls may be used to perform chip probe (CP) testing on the integrated circuit die 50. CP testing may be performed on the integrated circuit die 50 to ascertain whether the integrated circuit die 50 is a known good die (KGD). Thus, only integrated circuit dies 50, which are KGDs, undergo subsequent processing are packaged, and dies, which fail the CP testing, are not packaged. After testing, the solder regions may be removed in subsequent processing steps.

A dielectric layer 68 may (or may not) be on the active side of the integrated circuit die 50, such as on the passivation films 64 and the die connectors 66. The dielectric layer 68 laterally encapsulates the die connectors 66, and the dielectric layer 68 is laterally coterminous with the integrated circuit die 50. Initially, the dielectric layer 68 may bury the die connectors 66, such that the topmost surface of the dielectric layer 68 is above the topmost surfaces of the die connectors 66. In some embodiments where solder regions are disposed on the die connectors 66, the dielectric layer 68 may also bury the solder regions. Alternatively, the solder regions may be removed prior to forming the dielectric layer 68.

The dielectric layer 68 may be a polymer such as polybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or the like; a nitride such as silicon nitride or the like; an oxide such as silicon oxide, phosphosilicate glass (PSG), borosilicate glass (BSG), boron-doped phosphosilicate glass (BPSG), or the like; the like, or a combination thereof. The dielectric layer 68 may be formed, for example, by spin coating, lamination, chemical vapor deposition (CVD), or the like. In some embodiments, the die connectors 66 are exposed through the dielectric layer 68 during formation of the integrated circuit die 50. In some embodiments, the die connectors 66 remain buried and are exposed during a subsequent process for packaging the integrated circuit die 50. Exposing the die connectors 66 may remove any solder regions that may be present on the die connectors 66.

In some embodiments, the integrated circuit die 50 is a stacked device that includes multiple semiconductor substrates 52. For example, the integrated circuit die 50 may be a memory device such as a hybrid memory cube (HMC) device, a high bandwidth memory (HBM) device, or the like that includes multiple memory dies. In such embodiments, the integrated circuit die 50 includes multiple semiconductor substrates 52 interconnected by through-substrate vias (TSVs). Each of the semiconductor substrates 52 may (or may not) have an interconnect structure.

FIGS. 2 through 12 illustrate various views of intermediate steps during a process for forming a package component 100, in accordance with some embodiments. FIGS. 2, 3, 4, 5, 6, 7, 8, 9, 11, and 12 are cross-sectional views, and FIG. 10 is a top-down view. The package component 100 is a reconstructed wafer having multiple package regions, with one or more of the integrated circuit dies 50 being packaged in each of the package regions. The package regions include computing sites 101 and connecting sites 102. Each of the computing sites 101 may have e.g., logic functions, memory functions, or the like, and the package component 100 may be a single computing device comprising the computing sites 101 and connecting sites 102, such as a system-on-wafer (SoW) device. For example, the package component 100 may be an artificial intelligence (AI) accelerator, and each computing site 101 may be a neural network node for the AI accelerator. Each of the connecting sites 102 may have, e.g., external connectors, and the computing sites 101 of the package component 100 may connect to external systems through the connecting sites 102. Example systems for the package component 100 include AI servers, high-performance computing (HPC) systems, high power computing devices, cloud computing systems, edge computing systems, and the like. Two computing sites 101, e.g., computing sites 101A and 101B, and one connecting site 102, e.g., connecting site 102A, are illustrated, but it should be appreciated that the package component 100 may include many computing sites 101 and connecting sites 102, and the sites may be laid out in a variety of manners. Example layouts for the package component 100 are illustrated and discussed with respect to FIG. 10. FIGS. 2, 3, 4, 5, 6, 7, 8, 9, and 12 only show a portion of the package component 100, such as that indicated by cross-section A-A in FIG. 10.

In FIG. 2, a carrier substrate 103 is provided, and an adhesive layer 104 is formed on the carrier substrate 103. The carrier substrate 103 may be a glass carrier substrate, a ceramic carrier substrate, or the like. The carrier substrate 103 may be a wafer, such that multiple packages can be formed on the carrier substrate 103 simultaneously. The adhesive layer 104 may be removed along with the carrier substrate 103 from the overlying structures that will be formed in subsequent steps. In some embodiments, the adhesive layer 104 is any suitable adhesive, epoxy, die attach film (DAF), or the like, and is applied over the surface of the carrier substrate 103.

Integrated circuit dies 50 are then attached to the adhesive layer 104. A desired type and quantity of integrated circuit dies 50 are attached in each of the computing sites 101A and 101B and the connecting site 102A. In some embodiments, a first type of integrated circuit die, such as a SoC die 50A, is attached in each computing site 101A and 101B, and a second type of integrated circuit die, such as an I/O interface die 50B, is attached in the connecting site 102A. Although a single integrated circuit die 50 is illustrated in each site, it should be appreciated that multiple integrated circuit dies may be attached adjacent one another in some or all of the sites. When multiple integrated circuit dies are attached in each computing site 101A and 101B, they may be of the same technology node, or different technology nodes. For example, the integrated circuit dies 50 may include dies formed at a 10 nm technology node, dies formed at a 7 nm technology node, the like, or combinations thereof.

In FIG. 3, an encapsulant 106 is formed on and around the various components. After formation, the encapsulant 106 encapsulates the integrated circuit dies 50. The encapsulant 106 may be a molding compound, epoxy, or the like, and may be applied by compression molding, transfer molding, or the like. The encapsulant 106 may be applied in liquid or semi-liquid form and then subsequently cured. In some embodiments, the encapsulant 106 is formed over the carrier substrate 103 such that the integrated circuit dies 50 are buried or covered, and a planarization process is then performed on the encapsulant 106 to expose the die connectors 66 of the integrated circuit dies 50. Topmost surfaces of the encapsulant 106, die connectors 66, and dielectric layers 68 are coplanar after the planarization process. The planarization process may be, for example, a chemical-mechanical polish (CMP).

In FIGS. 4 through 6, a redistribution structure 108 having a fine-featured portion 108A and a coarse-featured portion 108B (see FIG. 6) is formed over the encapsulant 106 and integrated circuit dies 50. The redistribution structure 108 includes metallization patterns, dielectric layers, and under-bump metallurgies (UBMs). The metallization patterns may also be referred to as redistribution layers or redistribution lines. The redistribution structure 108 is shown as an example having six layers of metallization patterns. More or fewer dielectric layers and metallization patterns may be formed in the redistribution structure 108. If fewer dielectric layers and metallization patterns are to be formed, steps and process discussed below may be omitted. If more dielectric layers and metallization patterns are to be formed, steps and processes discussed below may be repeated. The fine-featured portion 108A and coarse-featured portion 108B of the redistribution structure 108 include metallization patterns and dielectric layers of differing sizes.

In FIG. 4, the fine-featured portion 108A of the redistribution structure 108 is formed. The fine-featured portion 108A of the redistribution structure 108 includes dielectric layers 110, 114, 118, and 122; and metallization patterns 112, 116, and 120. In some embodiments, the dielectric layers 114, 118 and 122 are formed from a same dielectric material, and are formed to a same thickness. Likewise, in some embodiments, the conductive features of the metallization patterns 112, 116 and 120 are formed from a same conductive material, and are formed to a same thickness. In particular, the dielectric layers 114, 118 and 122 have a first thickness T₁ that is small, such as in the range of about 7 μm to about 40 μm, and the conductive features of the metallization patterns 112, 116 and 120 have a second thickness T₂ that is small, such as in the range of about 2 μm to about 15 μm.

As an example of forming the fine-featured portion 108A of the redistribution structure 108, the dielectric layer 110 is deposited on the encapsulant 106, dielectric layers 68, and die connectors 66. In some embodiments, the dielectric layer 110 is formed of a photo-sensitive material such as PBO, polyimide, BCB, or the like, which may be patterned using a lithography mask. The dielectric layer 110 may be formed by spin coating, lamination, CVD, the like, or a combination thereof. The dielectric layer 110 is then patterned. The patterning forms openings exposing portions of the die connectors 66. The patterning may be by an acceptable process, such as by exposing the dielectric layer 110 to light when the dielectric layer 110 is a photo-sensitive material or by etching using, for example, an anisotropic etch. If the dielectric layer 110 is a photo-sensitive material, the dielectric layer 110 can be developed after the exposure.

The metallization pattern 112 is then formed. The metallization pattern 112 has line portions (also referred to as conductive lines or traces) on and extending along the major surface of the dielectric layer 110, and has via portions (also referred to as conductive vias) extending through the dielectric layer 110 to physically and electrically couple the die connectors 66 of the integrated circuit dies 50. As an example to form the metallization pattern 112, a seed layer is formed over the dielectric layer 110 and in the openings extending through the dielectric layer 110. In some embodiments, the seed layer is a metal layer, which may be a single layer or a composite layer comprising a plurality of sub-layers formed of different materials. In some embodiments, the seed layer comprises a titanium layer and a copper layer over the titanium layer. The seed layer may be formed using, for example, physical vapor deposition (PVD) or the like. A photoresist is then formed and patterned on the seed layer. The photoresist may be formed by spin coating or the like and may be exposed to light for patterning. The pattern of the photoresist corresponds to the metallization pattern 112. The patterning forms openings through the photoresist to expose the seed layer. A conductive material is then formed in the openings of the photoresist and on the exposed portions of the seed layer. The conductive material may be formed by plating, such as electroplating or electroless plating, or the like. The conductive material may comprise a metal, like copper, titanium, tungsten, aluminum, or the like. The combination of the conductive material and underlying portions of the seed layer form the metallization pattern 112. The photoresist and portions of the seed layer on which the conductive material is not formed are removed. The photoresist may be removed by an acceptable ashing or stripping process, such as using an oxygen plasma or the like. Once the photoresist is removed, exposed portions of the seed layer are removed, such as by using an acceptable etching process, such as by wet or dry etching.

The dielectric layer 114 is then deposited on the metallization pattern 112 and dielectric layer 110. The dielectric layer 114 may be formed in a similar manner and of a similar material as the dielectric layer 110. The metallization pattern 116 is then formed. The metallization pattern 116 has line portions on and extending along the major surface of the dielectric layer 114, and has via portions extending through the dielectric layer 114 to physically and electrically couple the metallization pattern 112. The metallization pattern 116 may be formed in a similar manner and of a similar material as the metallization pattern 112.

The dielectric layer 118 is then deposited on the metallization pattern 116 and dielectric layer 114. The dielectric layer 118 may be formed in a similar manner and of a similar material as the dielectric layer 110. The metallization pattern 120 is then formed. The metallization pattern 120 has line portions on and extending along the major surface of the dielectric layer 118, and has via portions extending through the dielectric layer 118 to physically and electrically couple the metallization pattern 116. The metallization pattern 120 may be formed in a similar manner and of a similar material as the metallization pattern 112.

The dielectric layer 122 is deposited on the metallization pattern 120 and dielectric layer 118. The dielectric layer 122 may be formed in a similar manner and of a similar material as the dielectric layer 110.

In FIG. 5, the coarse-featured portion 108B of the redistribution structure 108 is formed. The coarse-featured portion 108B of the redistribution structure 108 includes dielectric layers 126, 130, and 134; and metallization patterns 124, 128, and 132. In some embodiments, the dielectric layers 126, 130, and 134 are formed from a same dielectric material, and are formed to a same thickness. Likewise, in some embodiments, the conductive features of the metallization patterns 124, 128, and 132 are formed from a same conductive material, and are formed to a same thickness. In particular, the dielectric layers 126, 130, and 134 have a third thickness T₃ that is large, such as in the range of about 7 μm to about 40 μm, and the conductive features of the metallization patterns 124, 128, and 132 have a fourth thickness T₄ that is large, such as in the range of about 2 μm to about 15 μm. The third thickness T₃ is greater than the first thickness T₁ (see FIG. 4), and the fourth thickness T₄ is greater than the second thickness T₂ (see FIG. 4).

As an example of forming the coarse-featured portion 108B of the redistribution structure 108, the metallization pattern 124 is formed. The metallization pattern 124 is then formed. The metallization pattern 124 has line portions on and extending along the major surface of the dielectric layer 122, and has via portions extending through the dielectric layer 122 to physically and electrically couple the metallization pattern 120. As an example to form the metallization pattern 124, a seed layer is formed over the dielectric layer 122 and in the openings extending through the dielectric layer 122. In some embodiments, the seed layer is a metal layer, which may be a single layer or a composite layer comprising a plurality of sub-layers formed of different materials. In some embodiments, the seed layer comprises a titanium layer and a copper layer over the titanium layer. The seed layer may be formed using, for example, PVD or the like. A photoresist is then formed and patterned on the seed layer. The photoresist may be formed by spin coating or the like and may be exposed to light for patterning. The pattern of the photoresist corresponds to the metallization pattern 124. The patterning forms openings through the photoresist to expose the seed layer. A conductive material is then formed in the openings of the photoresist and on the exposed portions of the seed layer. The conductive material may be formed by plating, such as electroplating or electroless plating, or the like. The conductive material may comprise a metal, like copper, titanium, tungsten, aluminum, or the like. The combination of the conductive material and underlying portions of the seed layer form the metallization pattern 124. The photoresist and portions of the seed layer on which the conductive material is not formed are removed. The photoresist may be removed by an acceptable ashing or stripping process, such as using an oxygen plasma or the like. Once the photoresist is removed, exposed portions of the seed layer are removed, such as by using an acceptable etching process, such as by wet or dry etching.

The dielectric layer 126 is then deposited on the metallization pattern 124 and dielectric layer 122. In some embodiments, the dielectric layer 126 is formed of a photo-sensitive material such as PBO, polyimide, BCB, or the like, which may be patterned using a lithography mask. The dielectric layer 126 may be formed by spin coating, lamination, CVD, the like, or a combination thereof. The metallization pattern 128 is then formed. The metallization pattern 128 has line portions on and extending along the major surface of the dielectric layer 126, and has via portions extending through the dielectric layer 126 to physically and electrically couple the metallization pattern 124. The metallization pattern 128 may be formed in a similar manner and of a similar material as the metallization pattern 124.

The dielectric layer 130 is then deposited on the metallization pattern 128 and dielectric layer 126. The dielectric layer 130 may be formed in a similar manner and of a similar material as the dielectric layer 126. The metallization pattern 132 is then formed. The metallization pattern 132 has line portions on and extending along the major surface of the dielectric layer 130, and has via portions extending through the dielectric layer 130 to physically and electrically couple the metallization pattern 128. The metallization pattern 132 may be formed in a similar manner and of a similar material as the metallization pattern 124.

The dielectric layer 134 is deposited on the metallization pattern 132 and dielectric layer 130. The dielectric layer 134 may be formed in a similar manner and of a similar material as the dielectric layer 126.

In FIG. 6, UBMs 136 are formed for external connection to the redistribution structure 108. The UBMs 136 have bump portions on and extending along the major surface of the dielectric layer 134, and have via portions extending through the dielectric layer 134 to physically and electrically couple the metallization pattern 132. As a result, the UBMs 136 are electrically coupled to the integrated circuit dies 50. The UBMs 136 may be formed in a similar manner and of a similar material as the metallization pattern 132. In some embodiments, the UBMs 136 have a different size than the metallization patterns 112, 116, 120, 124, 128, and 132.

In FIG. 7, a carrier substrate debonding is performed to detach (or “debond”) the carrier substrate 103 from the encapsulant 106 and integrated circuit dies 50. In some embodiments, the debonding includes removing the carrier substrate 103 and adhesive layer 104 by, e.g., a grinding or planarization process, such as a CMP. After removal, back side surfaces of the integrated circuit dies 50 are exposed, and the back side surfaces of the encapsulant 106 and integrated circuit dies 50 are level. The structure is then placed on a tape 138.

In FIG. 8, conductive connectors 140 are formed on the UBMs 136. The conductive connectors 140 may be ball grid array (BGA) connectors, solder balls, metal pillars, controlled collapse chip connection (C4) bumps, micro bumps, electroless nickel-electroless palladium-immersion gold technique (ENEPIG) formed bumps, or the like. The conductive connectors 140 may include a conductive material such as solder, copper, aluminum, gold, nickel, silver, palladium, tin, the like, or a combination thereof. In some embodiments, the conductive connectors 140 are formed by initially forming a layer of solder or solder paste through evaporation, electroplating, printing, solder transfer, ball placement, or the like. Once a layer of solder has been formed on the structure, a reflow may be performed in order to shape the material into the desired bump shapes.

In FIG. 9, sockets 142 and connectors 143 are attached to the redistribution structure 108. The sockets 142 and connectors 143 are interfaces for external connection to the package component 100. The sockets 142 and connectors 143 include pads 144, such as aluminum pads, to which external connections are made. The sockets 142 and connectors 143 are mounted to the UBMs 136 using the conductive connectors 140. In the embodiment shown, the sockets 142 are attached at the computing sites 101A and 101B, and the connectors 143 are attached at the connecting site 102A. An underfill 146 is formed to fill the gaps between the sockets 142 and connectors 143 and the redistribution structure 108. The underfill 146 may be formed by a capillary flow process after the sockets 142 and connectors 143 are attached, or may be formed by a suitable deposition method before the sockets 142 and connectors 143 are attached.

The sockets 142 are electrical and physical interfaces for modules (discussed further below) that may be installed at the computing sites 101A and 101B subsequent to manufacture of the package component 100. For example, a user of the package component 100 may install modules in the sockets 142 to form completed functional systems at the computing sites 101A and 101B. The type of modules selected for installation depends on the type of functional systems desired at the computing sites 101A and 101B. Examples of modules that may be installed in the sockets 142 include memory modules, voltage regulator modules, power supply modules, integrated passive device (IPD) modules, and the like. The sockets 142 may include different components, such as a chassis and contact pins, which may comprise different materials. Although the sockets 142 are formed from multiple, differing materials, the sockets 142 collectively have an average stiffness, which can be quantified by their Yong's modulus. The sockets 142 have a high average stiffness, such as a Young's modulus that can be in the range of about 10 GPa to about 50 GPa. As discussed further below, subsequently formed overlying features have a lower average stiffness than the sockets 142.

The connectors 143 are electrical and physical interfaces for the package component 100 to external systems. For example, when the package component 100 is installed as part of a larger external system, such as a data center, the connectors 143 may be used to couple the package component 100 to the external system. Examples of connectors 143 include receptors for ribbon cables, flexible printed circuits, or the like.

The sockets 142 and connectors 143 may be attached to the redistribution structure 108 in a variety of layouts. The layout shown in FIG. 9 is one example. FIG. 10 is a top-down view of the package component 100. Each socket 142 directly overlies and is electrically coupled to the SoC dies 50A of a corresponding computing site 101A or 101B. The connectors 143 are disposed around the perimeter of the package component 100, thus increasing the area available for the sockets 142. The connecting site 102A may include one or more connectors 143. In the illustrated embodiment, the connectors 143 are laterally offset from the I/O interface dies 50B. In another embodiment, the connectors 143 directly overly the I/O interface dies 50B.

When the sockets 142 are attached to the redistribution structure 108, the conductive connectors 140 are reflowed to physically and electrically couple the pads 144 to the UBMs 136. FIG. 11 is a detailed view of a region 11 in FIG. 9, showing additional features of the sockets 142 after reflow. During the debonding of the carrier substrate 103 (see FIG. 7), warpage of the package component 100 occurs. Because the package component wo is warped, the attached sockets 142 may be tilted after the conductive connectors 140 are reflowed. In the example shown, one edge of a socket 142 is disposed a first distance D₁ from the redistribution structure 108, and an opposing edge of the socket 142 is disposed a greater second distance D₂ from the redistribution structure 108. Depending on the amount of warpage, the difference between the distances D₁ and D₂ can be large. For example, the difference between the distances D₁ and D₂ can be in the range of about 200 μm to about 400 μm. As discussed further below, the uneven heights of the tilted sockets 142 can decrease thermal dissipation for the package component 100 when a thermal spreading module is attached.

In FIG. 12, bolt holes 148 are formed through the package component 100. The bolt holes 148 may be formed by a drilling process such as laser drilling, mechanical drilling, or the like. The bolt holes 148 may be formed by drilling an outline for the bolt holes 148 with the drilling process, and then removing the material separated by the outline.

FIGS. 13 and 14 illustrate various view of a process for securing the package component 100 between a thermal module 200 and a mechanical brace 300, in accordance with some embodiments. The thermal module 200 may be a heat sink, a heat spreader, a cold plate, or the like. The mechanical brace 300 is a rigid support that may be formed from a material with a high stiffness, such as a metal, e.g., steel, titanium, cobalt, or the like. The mechanical brace 300 physically engages portions of the sockets 142, securing the sockets 142 when modules are installed or removed. Warpage of the package component 100, such as that induced by carrier substrate debonding, may be reduced by clamping the package component 100 between the thermal module 200 and mechanical brace 300. FIG. 13 is a three-dimensional view illustrating one quarter of the package component 100, thermal module 200, and mechanical brace 300 during assembly, in accordance with some embodiments. Some details are omitted in FIG. 13 for clarity of illustration. FIG. 14 is a cross-sectional view illustrating portions of the package component 100, thermal module 200, and mechanical brace 300 after assembly, and is described in conjunction with FIG. 13. FIG. 14 is illustrated along reference cross-section B-B in FIG. 13.

The package component 100 is removed from the tape 138 and is fastened between the thermal module 200 and mechanical brace 300 with bolts 202. The bolts 202 are threaded through the bolt holes 148 of the package component 100, through corresponding bolt holes 204 in the thermal module 200, and through corresponding bolt holes 302 in the mechanical brace 300. Fasteners 206 are threaded onto the bolts 202 and tightened to clamp the package component 100 between the thermal module 200 and mechanical brace 300. The fasteners 206 may be, e.g., nuts that thread to the bolts 202. The fasteners 206 attach to the bolts 202 at both sides of the resulting system-on-wafer assembly (e.g., at the side having the thermal module 200 (sometimes referred to as the back side) and at the side having the mechanical brace 300 (sometimes referred to as the front side)).

Before fastening together the various components, a thermal interface material (TIM) 208 (see FIG. 14) is dispensed on the back side of the package component 100, physically and thermally coupling the thermal module 200 to the integrated circuit dies 50. During fastening, the fasteners 206 are tightened, thereby increasing the mechanical force applied to the package component 100 by the thermal module 200 and the mechanical brace 300. The fasteners 206 are tightened until the thermal module 200 exerts a desired amount of pressure on the TIM 208. For example, the tightening of the fasteners 206 may be performed with a torque in the range of about 20 N·m to about 30 N·m. The TIM 208 may be formed of a metal or metal paste. In some embodiments, the TIM 208 is formed of a film comprising indium and an HM03 type material.

The mechanical brace 300 has openings 304 exposing portions of the sockets 142, for ease of module installation. The edge regions of the mechanical brace 300, such as edge regions of the outermost periphery and edge regions of the openings 304, physically engage and overlap with edge regions of the sockets 142. In some embodiments, the mechanical brace 300 only engages some edge regions of the sockets 142.

The mechanical brace 300 further includes screw holes 306 disposed around the openings 304. FIGS. 15 and 16 illustrate aspects of the mechanical brace 300, in accordance with various embodiments. FIG. 15 is a top-down view of a mechanical brace 300. The screw holes 306 are disposed around peripheries of each opening 304, e.g., in the edge regions of the mechanical brace 300 proximate each opening 304. The screw holes 306 may be smaller than the bolt holes 302. For example, the bolt holes 302 can have a diameter in the range of about 3 mm to about 5 mm, and the screw holes 306 can have a diameter in the range of about 2 mm to about 3 mm. Further, the screw holes 306 are threaded, while the bolt holes 302 may be unthreaded, e.g., smooth. FIG. 16 is a three-dimensional view of a mechanical brace 300, showing the fastening of standoff screws 308 in the screw holes 306. The standoff screws 308 are fastened in the screw holes 306 before the package component 100 is clamped between the thermal module 200 and mechanical brace 300. As discussed further below, the standoff screws 308 help compensate for differences in heights of the sockets 142 when then mechanical brace 300 engages the sockets 142 during clamping. The mechanical brace 300 may thus engage more of the edges of the sockets 142.

In the embodiment of FIGS. 15 and 16, each edge of the openings 304 has a group of two screw holes 306. In other embodiments, such as the embodiment of FIG. 13, the groups of screw holes 306 around the edges of the openings 304 may have more or less screw holes 306. The openings 304 are spaced apart a distance D₃, which in some embodiments, can be in the range of about 4 mm and about 10 mm, such as about 10 mm. The screw holes 306 around the edges of the openings 304 in a same group are spaced apart a distance D₄, which in some embodiments, can be in the range of about 5 mm and about 10 mm, or can be about 12.6 mm. The screw holes 306 are disposed a distance D₅ from edges of the openings 304, which in some embodiments, can be in the range of about 15 mm and about 17 mm, or can be about 2.5 mm. Each group of screw holes 306 is disposed a distance D₆ from the adjoining perpendicular edges of the openings 304, which in some embodiments, can be in the range of about 3 mm and about 6 mm, such as about 3.6 mm.

FIGS. 17A and 17B illustrate a standoff screw 308, in accordance with some embodiments. FIG. 17A shows a perspective view of a first end of the standoff screw 308, and FIG. 17B shows a perspective view of an opposing second end of the standoff screw 308. The standoff screw 308 includes a soft tip 310 at the first end, and a head 312 at the second end. The soft tip 310 may comprise a rubber such as silicone. The head 312 is recessed into the main body of the standoff screw 308, and may have any shape, such as a hexagon, a star, or the like. The standoff screws 308 may be machine screws, such as stop screws. The standoff screws 308 may be any size, and in one example, are M2.5 stop screws. The standoff screws 308 may be formed from a metal such as Cr—Mo alloy steel, e.g., SCM435 steel. The steel may have any grade, and in one example, has a grade of 12.9.

FIGS. 18A, 18B, and 18C illustrate cross-sections of the standoff screws 308, in accordance with various embodiments. The soft tips 310 of the standoff screws 308 may have one of several possible shapes in the cross-sectional views. In the embodiment of FIG. 18A, the soft tips 310 have sidewalls spaced apart by a constant width. In the embodiment of FIG. 18B, the soft tips 310 have tapered sidewalls spaced apart by a continually decreasing width. In the embodiment of FIG. 18C, the soft tips 310 have stepped sidewalls spaced apart by a plurality of discrete distances. The soft tips 310 of the standoff screws 308 may also have one of several possible shapes in a top-down view. For example, the soft tips 310 may be round, square, hexagonal, or the like in a top-down view. The soft tips 310 can have any thickness T₅, such as a thickness T₅ in the range of about 0.5 mm to about 2 mm, such as about 1 mm. The main body of the standoff screw 308 can have any thickness T₆, such as a thickness T₆ in the range of about 2 mm to about 7 mm, such as about 2 mm. The thickness T₆ is greater than the thickness T₅.

As noted above, the sockets 142 may be tilted after they are attached. FIG. 19 is a detailed view of a region 19 in FIG. 14, showing additional features of the sockets 142. Because the sockets 142 are tilted, a gap G₁ is formed between the mechanical brace 300 and edges of the tilted sockets 142, where the length of each gap G₁ is equal to the difference between the distances D₁ and D₂. The standoff screws 308 may be adjusted so that each standoff screw 308 extends a distance out of its screw hole 306 equal to the length of the overlying gap G₁. As such, each adjusted standoff screw 308 contacts its respective socket 142 when the mechanical brace 300 is clamped to the package component 100. Before adjusting the standoff screws 308, each standoff screws 308 is disposed an initial distance from the respective socket 142. Adjusting the standoff screws 308 reduces that distance.

A socket 142 may be contacted by multiple standoff screws 308 after the adjusting. In some embodiments, all of the standoff screws 308 around a given opening 304 are adjusted to contact the socket 142 exposed by that opening 304. In some embodiments, only some of the standoff screws 308 around a given opening 304 are adjusted to contact the socket 142 exposed by that opening 304, and some edges of that socket 142 physically contact the mechanical brace 300 without requiring adjustment of the remaining standoff screws 308. In other words, in some embodiments, a first edge of an opening 304 may contact the socket 142 exposed by that opening 304, and a second edge of the opening 304 may be physically separated from the socket 142 by the standoff screw(s) 308 at that edge.

In some embodiments, the fasteners 206 are initially tightened using a small amount of torque. For example, the initial tightening may be performed with a torque in the range of about 5 N·m to about 10 N·m. As such, after the initial tightening process, the mechanical brace 300 is secured in place, but is not yet exerting the desired amount of pressure on the TIM 208. Each of the standoff screws 308 may then be adjusted to close the gap G₁ between the mechanical brace 300 and corresponding sockets 142. Adjusting the standoff screws 308 includes inserting a wrench or screwdriver into the heads 312 of the standoff screws 308 and turning the standoff screws 308. The threading of the standoff screws 308 and screw holes 306 causes the gap G₁ between the mechanical brace 300 and corresponding socket 142 to be varied when the standoff screws 308 are turned in their screw holes 306. After the standoff screws 308 are adjusted, the fasteners 206 are finally tightened using a larger amount of torque. For example, the final tightening may be performed with a torque in the range of about 20 N·m to about 30 N·m. After the final tightening process, the mechanical brace 300 is secured in place and exerts a desired amount of pressure on the TIM 208. For example, the fasteners 206 may be tightened until the TIM 208 undergoes at least 60 pounds per square inch (PSI) of pressure, such as about 65 PSI. Exerting at least 60 PSI of pressure on the TIM 208 may decrease the thermal resistance of the TIM 208, increasing thermal dissipation for the package component 100. The adjusted standoff screws 308 help evenly distribute the pressure across the TIM 208 at the computing sites 101A and 101B. Thermal dissipation at the computing sites 101A and 101B may thus be improved. Further, a high pressure also causes the mechanical brace 300 to exert force on the package component 100, thereby reducing warpage of the package component 100.

FIG. 20 illustrates a cross-sectional view of the resulting system-on-wafer assembly after modules 400 are installed in the sockets 142. FIG. 20 is illustrated along reference cross-section B-B in FIG. 13. As noted above, the modules 400 may be memory modules, voltage regulator modules, power supply modules, integrated passive device (IPD) modules, and the like. The modules 400 comprise conductive connectors 402, which are inserted in corresponding receptors to physically and electrically couple the contact pins of the sockets 142. The modules 400 are thus secured in the sockets 142, forming completed functional systems at the computing sites 101A and 101B. After installation, the modules 400 are disposed in the openings 304 of the mechanical brace 300.

Other features and processes may also be included. For example, testing structures may be included to aid in the verification testing of the 3D packaging or 3DIC devices. The testing structures may include, for example, test pads formed in a redistribution layer or on a substrate that allows the testing of the 3D packaging or 3DIC, the use of probes and/or probe cards, and the like. The verification testing may be performed on intermediate structures as well as the final structure. Additionally, the structures and methods disclosed herein may be used in conjunction with testing methodologies that incorporate intermediate verification of known good dies to increase the yield and decrease costs.

Embodiments may achieve advantages. Installing the standoff screws 308 in the mechanical brace 300 and adjusting the standoff screws 308 until they contact their respective sockets 142 help increase the uniformity of pressure applied when the fasteners 206 are tightened to clamp the package component 100 between the thermal module 200 and mechanical brace 300. A more uniform pressure may improve the thermal conductivity of the TIM 208. The thermal dissipation of the package component 100 may thus be improved.

In an embodiment, a device includes: an integrated circuit die; a redistribution structure over a front-side surface of the integrated circuit die; a socket over the redistribution structure; a mechanical brace over the socket, the mechanical brace having an opening exposing the socket, edge regions of the socket overlapping edge regions of the mechanical brace at the opening; a first standoff screw disposed in the edge regions of the mechanical brace, the first standoff screw physically contacting the socket, the first standoff screw extending a first distance between the socket and the mechanical brace; and a bolt extending through the mechanical brace and the redistribution structure.

In some embodiments, the device further includes: a thermal interface material on a back-side surface of the integrated circuit die; and a thermal module thermally and physically coupled to the back-side surface of the integrated circuit die with the thermal interface material, the bolt extending through the thermal module and the thermal interface material. In some embodiments, the device further includes: a second standoff screw disposed in the edge regions of the mechanical brace, the second standoff screw physically contacting the socket, the second standoff screw extending a second distance between the socket and the mechanical brace, the second distance being greater than the first distance. In some embodiments of the device, the first standoff screw has a first diameter and the bolt has a second diameter, the second diameter being greater than the first diameter. In some embodiments, the first diameter is in a range of from 2 mm to 3 mm, and the second diameter is in a range of from 3 mm to 5 mm. In some embodiments of the device, the first standoff screw includes a main body, a rubber tip at a first end of the main body, and a head recessed into a second end of the main body, the rubber tip physically contacting the socket. In some embodiments of the device, the rubber tip has sidewalls spaced apart by a constant width. In some embodiments of the device, the rubber tip has tapered sidewalls spaced apart by a continually decreasing width. In some embodiments of the device, the rubber tip has stepped sidewalls spaced apart by a plurality of discrete distances.

In an embodiment, a method includes: forming a package component including an integrated circuit die, a redistribution structure over the integrated circuit die, and a socket over the redistribution structure; assembling the package component between a thermal module and a mechanical brace with a bolt extending through the thermal module, the package component, and the mechanical brace, the mechanical brace including a standoff screw disposed a first distance from the socket after the assembling; tightening a fastener on the bolt with a first amount of torque; adjusting the standoff screw to reduce the first distance between the standoff screw and the socket; and after adjusting the standoff screw, tightening the fastener on the bolt with a second amount of torque, the second amount of torque being greater than the first amount of torque.

In some embodiments of the method, assembling the package component includes dispensing a thermal interface material on the package component, the thermal interface material physically and thermally coupling the integrated circuit die of the package component to the thermal module after the assembling. In some embodiments of the method, the first amount of torque is in a range of 5 N·m to 10 N·m, and the second amount of torque is in a range of 20 N·m to 30 N·m. In some embodiments of the method, the mechanical brace has an opening exposing the socket, edges of the socket overlapping edges of the mechanical brace at the opening, the standoff screw being disposed at one of the edges of the opening in the mechanical brace. In some embodiments of the method, after the assembling, a first one of the edges of the opening contacts the socket, and a second one of the edges of the opening is physically separated from the socket. In some embodiments of the method, the standoff screw is one of a plurality of standoff screws disposed at the edges of the opening in the mechanical brace. In some embodiments of the method, two standoff screws are disposed at each of the edges of the opening in the mechanical brace. In some embodiments of the method, the standoff screw includes a main body, a rubber tip at a first end of the main body, and a head recessed into a second end of the main body; where after adjusting the standoff screw, the rubber tip contacts the socket. In some embodiments, the method further includes: after tightening the fastener on the bolt with the second amount of torque, installing a module in the socket.

In an embodiment, a method includes: encapsulating an integrated circuit die with an encapsulant; forming a redistribution structure over the encapsulant and the integrated circuit die; attaching a socket to the redistribution structure; screwing a standoff into a mechanical brace; bolting the mechanical brace to the redistribution structure, the mechanical brace physically contacting a first edge of the socket, the mechanical brace being physically separated from a second edge of the socket; and adjusting height of the standoff until the standoff physically contacts the second edge of the socket.

In some embodiments of the method, the standoff includes a main body and a rubber tip, the rubber tip physically contacting the second edge of the socket after adjusting the height of the standoff.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method comprising: forming a package component comprising an integrated circuit die, a redistribution structure over the integrated circuit die, and a socket over the redistribution structure; assembling the package component between a thermal module and a mechanical brace with a bolt extending through the thermal module, the package component, and the mechanical brace, the mechanical brace comprising a standoff screw disposed a first distance from the socket after the assembling; tightening a fastener on the bolt with a first amount of torque; adjusting the standoff screw to reduce the first distance between the standoff screw and the socket; and after adjusting the standoff screw, tightening the fastener on the bolt with a second amount of torque, the second amount of torque being greater than the first amount of torque.
 2. The method of claim 1, wherein assembling the package component comprises dispensing a thermal interface material on the package component, the thermal interface material physically and thermally coupling the integrated circuit die of the package component to the thermal module after the assembling.
 3. The method of claim 1, wherein the first amount of torque is in a range of 5 N·m to 10 N·m, and the second amount of torque is in a range of 20 N·m to 30 N·m.
 4. The method of claim 1, wherein the mechanical brace has an opening exposing the socket, edges of the socket overlapping edges of the mechanical brace at the opening, the standoff screw being disposed at one of the edges of the opening in the mechanical brace.
 5. The method of claim 4, wherein after the assembling, a first one of the edges of the opening contacts the socket, and a second one of the edges of the opening is physically separated from the socket.
 6. The method of claim 4, wherein the standoff screw is one of a plurality of standoff screws disposed at the edges of the opening in the mechanical brace.
 7. The method of claim 6, wherein two standoff screws are disposed at each of the edges of the opening in the mechanical brace.
 8. The method of claim 1, wherein the standoff screw comprises a main body, a rubber tip at a first end of the main body, and a head recessed into a second end of the main body, and wherein after adjusting the standoff screw, the rubber tip contacts the socket.
 9. The method of claim 1 further comprising: after tightening the fastener on the bolt with the second amount of torque, installing a module in the socket.
 10. A method comprising: encapsulating an integrated circuit die with an encapsulant; forming a redistribution structure over the encapsulant and the integrated circuit die; attaching a socket to the redistribution structure; screwing a standoff into a mechanical brace; bolting the mechanical brace to the redistribution structure, the mechanical brace physically contacting a first edge of the socket, the mechanical brace being physically separated from a second edge of the socket; and adjusting a height of the standoff until the standoff physically contacts the second edge of the socket.
 11. The method of claim 10, wherein the standoff comprises a main body and a rubber tip, the rubber tip physically contacting the second edge of the socket after adjusting the height of the standoff.
 12. The method of claim 11, wherein the rubber tip has sidewalls spaced apart by a constant width.
 13. The method of claim 11, wherein the rubber tip has tapered sidewalls spaced apart by a continually decreasing width.
 14. The method of claim 11, wherein the rubber tip has stepped sidewalls spaced apart by a plurality of discrete distances.
 15. The method of claim 10 further comprising: after adjusting the height of the standoff, increasing pressure exerted by the mechanical brace on the redistribution structure.
 16. A method comprising: screwing a first end of a standoff screw into a mechanical brace; placing the mechanical brace on a front-side of a package component, the package component comprising a socket; placing a thermal module on a back-side of the package component; fastening the thermal module to the mechanical brace with a bolt, the fastening comprising tightening a fastener on the bolt with a first amount of torque; adjusting the standoff screw, a second end of the standoff screw contacting the socket; and after the adjusting, tightening the fastener on the bolt with a second amount of torque, the second amount of torque being greater than the first amount of torque.
 17. The method of claim 16, wherein placing the thermal module on the back-side of the package component comprises dispensing a thermal interface material on the back-side of the package component, the thermal module exerting a first amount of pressure on the thermal interface material before the adjusting, the thermal module exerting a second amount of pressure on the thermal interface material after the adjusting.
 18. The method of claim 16, wherein the mechanical brace has an opening, a first portion of the mechanical brace at edges of the opening laterally overlapping edges of the socket.
 19. The method of claim 18 further comprising: screwing a plurality of standoff screws into the first portion of the mechanical brace, the standoff screw being one of the plurality of standoff screws; and adjusting the plurality of standoff screws, a subset of the plurality of standoff screws contacting the socket after the adjusting.
 20. The method of claim 18 further comprising: screwing a plurality of standoff screws into the first portion of the mechanical brace, the standoff screw being one of the plurality of standoff screws; and adjusting the plurality of standoff screws, each of the plurality of standoff screws contacting the socket after the adjusting. 